Report Manager supports automatic internacionalization and localization it will show the forms in the language selected by the user, that is LANG enviroment variable in Linux or Regional configuration in Microsoft Windows. This is only possible if you provide the translated resourcestring file for the selected language, if you don't provide it then the english language is selected.
The resource file is reportmanres.*, where * means the user selected language, for example reportmanres.es for Spanish based languages. The engine will search this file in the current dir so you must provide them when deploying your applications or Report Manager Designer.
To translate the resourcestrings you must download the translation kit (for now only supports Microsoft Windows, but the translated file is platform independent), it includes rptranslate.exe.
You must execute rptranslate.exe, open the reportmanres.en file located at Report Manager Designer directory and save as reportman.* where * is the destination language, then you can begin the translation. You can see a list of languages and their extensions, you must get the first two letters of the extension.
You can translate the translator itself using the same procedure with rptranslateres.en file.
If you don't know your language extension you can examine the avaliable extensions using the Language information item in utilities menu.